Barbara/Brainless is right and your vet is wrong: Panacur DOES protect against lungworm - not only that, but it protects against it *more effectively* than Advocate does. This is demonstrated in this research paper, which I'd suggest you print out and show your vet:
http://www.ncbi.nlm.nih.gov/pubmed/17544583(Fenbendazole is Panacur and imidacloprid/moxidectin spot-on is Advocate.)
Panacur's own leaflet/instructions do not state that it protects against Angiostrongylus vasorum, only against another lungworm (oscilirides or something) - however as is obvious from that research paper, Panacur DOES treat the lungworm everyone's worried about in the UK (Angiostrongylus vasorum). They just have not updated their leaflet and gotten on the lungworm marketing bandwagon, as Advocate has.
You do need to give a 7 day dose of it, as per the instructions.
And then there is another wormer - Milbemax - which you can give a one-off dose of, and that also covers lungworm. But be careful if you have a collie breed as it contains milbemycine oxime which collies can't tolerate.
I'm sick and tired of vets promoting Advocate as the only preventative for lungworm when it isn't. It is about their own ignorance and about marketing and money.